GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    •  Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B1325 03 : Device Power 1 Circuit Voltage Below Threshold

DTC B1325 07: Device Power 1 Circuit Voltage Above Threshold

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

B+

B1325 03

B1325 03

--

--

Ground

--

B1325 03

--

--

Circuit/System Description

The body control module (BCM) monitors the battery voltage through the battery voltage signal circuit. If the BCM senses that battery voltage is outside of its normal range, DTC  B1325 will set. Damage to components, and incorrect data may occur when the voltage is out of range.

Conditions for Running the DTC

    • The voltage supplied to the BCM are in the range of 7-26 volts.
    • The ignition is ON.
    • The engine is running.

Conditions for Setting the DTC

B1325 03

The BCM detects a system voltage less than 9 volts for 5 seconds.

B1325 07

The BCM detects a system voltage greater than 18 volts for 5 seconds.

Action Taken When the DTC Sets

    • The BCM immediately disables all outputs when an out of range voltage condition has been detected, with the exception of serial data and Run/Crank relay that are disabled after a 3 minute delay.
    • The setting of other DTCs is inhibited.

Conditions for Clearing the DTC

The DTC clears when the system voltage returns to a normal range.

Diagnostic Aids

    • A high or low voltage DTC set in multiple modules indicates a concern in the charging system.
    • A possible cause of this DTC could be overcharging with a battery charger or jump starting.
    • A high or low voltage value in multiple modules indicates a concern in the charging system.

Reference Information

Schematic Reference

Body Control System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Charging System Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Engine running measure and record the voltage at the battery terminals. Verify that the battery voltage is 12.6-15.5  volts.
  2. If the battery voltage is not within the specified range, refer to Charging System Test
  3. Engine running, observe the scan tool BCM Battery Positive Voltage parameter. The reading should be between 12.6 and 15.5 volts.

Circuit/System Testing

  1. Ignition OFF. Disconnect the harness connectors at the BCM.
  2. Test for less than 3.0  ohms between the ground circuits terminals listed below and ground.
  3. • Terminal 12 X1
    • Terminal  E2 X4
    If greater than the specified value, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify a test lamp illuminates between the B+ circuit terminals listed below and ground.
  5. • Terminal  D6 X3
    • Terminal  D1 X3
    If test lamp did not illuminate, test the B+ circuits for a short to ground or an open/high resistance.
  6. If all the circuits test normal, replace the BCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM replacement, setup, and programming.